Integrated optical switches have been widely used recently. To divert light from one waveguide to another, the waveguides are coupled by specific geometric arrangements of the two waveguides in relation to each other, where the coupling is modified by local electro-optical manipulation of their indices of refraction. Typical examples of electro-optical switches include the Mach-Zehnder interferometer 2×2 switch, the directional coupler 2×2 switch, the modal-interference 2×2 switch (e.g., two-mode interference switch, bifurcation optical active switch), the mode-evolution 2×2 switch, the imbalanced y-branch 1×2 switch, the digital-optical switch, and the total internal reflection (TIR) X-switch. Depending on the voltage applied to such switches or in some cases the electrical current actually, light is thus partly or completely diverted from an input waveguide to an output waveguide.
By appropriately combining waveguides and switches, a switch fabric (also referred to as switch matrix) is formed to switch light from multiple input waveguides among multiple output waveguides. A variety of switch fabric geometries have been used. Switch fabrics based on geometries such as crossbar geometry can be used to divert input signals to output channels arbitrarily. Signals from any input channels can be directed to any output channel, and even to multiple output channels, in broadcast and multicast transmission modes.
A typical switch employs the thermo-optic effect in a localized manner to control the refractive index within polymer waveguide structures to switch and attenuate the optical signals, which may limit the switching speed of the switch. Further, there has been a lack of commercially available switches possessing microsecond operation that have integrated variable optical attenuators and integrated optical power monitoring. The lack of integrated power monitoring means external components are required, which makes the overall approach more cumbersome and bulky.